Solar-Powered Drones’ can fly for hours, months, or even years

What happens when you pair up unmanned aerial vehicles (UAVs) with the very latest in photovoltaic cells? The result is two new UAV prototypes: an upgraded battlefield microdrone with more than four times the normal air endurance, and a giant, high-altitude “atmospheric satellite” that can fly months, even years at a time.

This week at the annual Association for Unmanned Vehicle Systems International (AUVSI) conference in Washington, D.C., California dronemaker AeroVironment unveiled a new version of its hand-thrown, 13-pound Puma AE—this one with gallium arsenide solar cells layering its wings and test-flown for more than 9 hours.

That’s a far cry from the standard Puma AE, which is currently in service with the U.S. military and has an air endurance of 2 hours. “The desire to extend the range on the small UAVs is something that we hear quite often from the customers,” explains David Heidel, marketing manager for AeroVironment’s unmanned aircraft systems (UAS) business. And now they have that extended range.

The secret behind the new 9-hour endurance is the flexible, high-efficiency gallium arsenide cells, says Rich Kapusta, marketing VP at solar-power partner Alta Devices. Earlier attempts by other companies to build solar-powered microdrones, such as Bye Aerospace and its Silent Falcon, have been stymied by low-efficiency silicon, he contends.

By contrast, the new solar Puma could be production-ready in early 2014. “And the beauty of this is we could offer this as a retrofit, an upgrade kit, so it’s not’s like customers already using the Puma would have to buy a whole new system,” Heidel adds.

In another stab at unmanned solar aviation, Titan Aerospace, a small Series A startup from New Mexico, is developing the SOLARA 50, a long-winged plane that will stay aloft for five years at a time, reaching an altitude of 65,000 feet. Titan Aerospace VP Stephen “Ron” Olsen calls the SOLARA 50 an atmospheric satellite and argues that, with a projected cost of less than $10 million, it will be a cheaper, retrievable alternative to conventional satellites.

Though reluctant to talk about specific technologies (for fear, he says, of competitors getting a jump on the startup), Olsen does wax excitedly about the many future applications of the high-flying, solar-powered UAV, including tracking wildlife, mapping fire, patrolling the U.S.–Mexico border, and even providing cellphone coverage to remote areas. “One of these [UAVs] at 10 miles can replace 100 cell towers,” he says.

The company has already tested in the skies above Moriarty, N.M., a small-scale, proof-of-concept vehicle with a 33-foot wingspan, and Titan Aerospace plans more, longer endurance testing in the near future, says chief mechanical engineer Daniel Cornew. The crowning achievement of this effort, scheduled for mid-2014, will be producing the SOLARA 50, which will weigh 400 pounds and have a 162-foot wingspan.

The idea of high-altitude, extreme-endurance solar UAVs goes back to the 1980s. And in the past 10 years, a few companies have come very close to making it a reality. AeroVironment, for example, developed the Helios prototype for NASA, but a catastrophic air mishap in 2003 cut that program short. Likewise, Boeing was making progress on the SolarEagle when the Defense Advanced Research Projects Agency (DARPA) scaled back its funding last year.

Though some might be discouraged by these failures, the folks at Titan Aerospace believe the relevant technologies—advanced composites, efficient solar cells and lithium batteries—are now mature enough to justify another go at an atmospheric satellite. “We came at the right moment in the timeline,” says Cornew. “We are now at the stage that a solar UAV is an assembly job, not an experiment.”